It is well known that iron elements used, for instance, for manufacturing reinforcements for reinforced concrete can be obtained from bar-shaped steel rods. To this end, the bars are fed, individually or bunched, to operating machines that automatically manufacture the bars in a series of desired products. The plants intended for manufacturing such metallic section bars are usually provided with a depository, known as ironworks, from which the bars are methodically stored and, little by little, taken and fed to the operating machines or merely moved elsewhere.
Furthermore, it is a necessity to evaluate the correct number of bars to take or to feed to the operating machine depending on the manufacturing requirements, for instance according to the production capacity of the machines, the diameter of the bars, the peculiarities of the processed material, the production requirements.
Several methods and related apparatuses have been proposed for taking and feeding metallic section bars.
The European patent EP 0790086 illustrates a method for the automatic separation of metallic bars. According to this method, metallic bars, packed in a bundle, are repeatedly lowered and lifted, at least near respective ends, in such a way that at least a couple of ends is retained at a lifted position. Detecting instruments of optoelectronic type detect the position of the bars, so that at least a metallic bar can be selected in a suitable position for the subsequent separation. Afterwards, a gripping device is positioned at the end portion of the selected bar in order to operate the locking, the horizontal shifting and eventually the separation from the remaining metallic bars. Subsequently, the singularized bar can be laid on a supporting surface or fed to a successive processing station.
Such a method appears very complicated because it requires the use of sophisticated detecting instruments in order to operate the selection of every metallic bar to separate. Furthermore, the preliminary operations to the selection, particularly the repeated lowering and lifting of the bundle of bars, remarkably extend the production time needed for every separation cycle.
The U.S. Pat. No. 4,548,537 illustrates an apparatus suited to collect one by one different bar-shaped materials initially stored on a shelf. A portion of the bars is separated from the heap by means of collecting means located near the shelf, so as to be seized by vicing means contrasting the collecting means. Afterwards, the bars, retained by the vicing means, are extracted by extracting means and separated from the remaining material stored on the shelf
Such an apparatus appears extremely slow, because only a single bar is separated at every cycle performed by the collecting means. Furthermore, it can be used only with very stiff bars, preferably short, or with pipes which are unlikely to get entangled during the storing phase. On the contrary, the apparatus cannot be effectively used with iron rods for reinforced concrete, which, owing to their length, generally variable from 12 to 24 meters, show a considerable flexibility.
The Italian patent application UD2004A000012 shows a separation apparatus including first magnetic tools acting along a first operating direction in order to separate and lift up from the bundle an end portion of a plurality of bars in store, disposing them substantially lined up on a surface. Second magnetic tools, acting along an operating direction substantially perpendicular to the longitudinal profile of the bars, are suited to collect and extract one or more bars at a time.
Apparatuses of such a typology show remarkable limitations because, being suited to seize single bars by only one end portion instead of by the whole length, they are suitable for use solely within machines provided with extracting and drawing means acting on the bars separated from the stored bundles. The patent application BO2002A000241, filed by the Applicant, belongs to such a typology as well.
The patent application BO2003A000039, filed by the Applicant, illustrates a method for feeding metallic section bars, which allows separating the correct number of bars from the bundle to which the separated bars belong, for automatically feeding such bars to the manufacturing plants. The method provides to seize a group of bars from a store of such bars and to transfer the aforesaid group of bars in a lifted position. The lifted bars are placed on a mobile transferring device provided with separation means of the kind of the Archimedean screw, whereat is operated the transversal transfer and the counting of a prearranged number of bars to feed at each cycle to the machine downstream. Such a method, however, causes relatively long operating times in comparison with the present production requirements.